title: Age of red blood cells and outcome in acute kidney injury.
abstract: BACKGROUND
  Transfusion of red blood cells (RBCs) and, in particular, older RBCs has been associated with increased short-term mortality in critically ill patients. We evaluated the association between age of transfused RBCs and acute kidney injury (AKI), hospital, and 90-day mortality in critically ill patients.
  
  
  METHODS
  We conducted a prospective, observational, predefined sub-study within the FINNish Acute Kidney Injury (FINNAKI) study. This study included all elective ICU admissions with expected ICU stay of more than 24 hours and all emergency admissions from September to November 2011. To study the age of RBCs, we classified transfused patients into quartiles according to the age of oldest transfused RBC unit in the ICU. AKI was defined according to KDIGO (Kidney Disease: Improving Global Outcomes) criteria.
  
  
  RESULTS
  Out of 1798 patients, 652 received at least one RBC unit. The median [interquartile range] age of the oldest RBC unit transfused was 12 [11-13] days in the freshest quartile and 21 [17-27] days in the quartiles 2 to 4. On logistic regression, RBC age was not associated with the development of KDIGO stage 3 AKI. Patients in the quartile of freshest RBCs had lower crude hospital and 90-day mortality rates compared to those in the quartiles of older blood. After adjustments, older RBC age was associated with significantly increased risk for hospital mortality. Age, Simplified Acute Physiology Score II (SAPS II)-score without age points, maximum Sequental Organ Failure Assessment (SOFA) score and the total number of transfused RBC units were independently associated with 90-day mortality.
  
  
  CONCLUSIONS
  The age of transfused RBC units was independently associated with hospital mortality but not with 90-day mortality or KDIGO stage 3 AKI. The number of transfused RBC units was an independent risk factor for 90-day mortality.
authors.forename: Kirsi-Maija
authors.initials: KM
authors.lastname: Kaukonen
authors.forename: Suvi T
authors.initials: ST
authors.lastname: Vaara
authors.forename: Ville
authors.initials: V
authors.lastname: Pettilä
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
authors.forename: Jarno
authors.initials: J
authors.lastname: Tuimala
authors.forename: David J
authors.initials: DJ
authors.lastname: Cooper
authors.forename: Tom
authors.initials: T
authors.lastname: Krusius
authors.forename: Anne
authors.initials: A
authors.lastname: Kuitunen
authors.forename: Matti
authors.initials: M
authors.lastname: Reinikainen
authors.forename: Juha
authors.initials: J
authors.lastname: Koskenkari
authors.forename: Ari
authors.initials: A
authors.lastname: Uusaro
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000401:mortality / Q000628:therapy*; D000368:Aged; D016638:Critical Illness; D004905:Erythrocyte Aging; D017707:Erythrocyte Transfusion / Q000401:mortality; D005260:Female; D005387:Finland / Q000453:epidemiology; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors